The present invention relates generally to imaging systems. More particularly, the present invention relates to an imaging system configured to track an image data receiver included therein to generate improved images.
When an object of interest, such as human tissue, is subjected to a uniform magnetic field (polarizing field Bo, along the z-direction in a Cartesian coordinate system denoted as x, y, and z), the individual magnetic moments of the spins in the tissue attempt to align with this polarizing field, but precess about it at their characteristic Larmor frequency. If such an object of interest, or tissue, is further subjected to a magnetic field (excitation field B1) which is in the x-y plane and which is near the Larmor frequency, the net aligned moment (Mz,) may be rotated or xe2x80x9ctippedxe2x80x9d at a certain tipping angle into the x-y plane to produce a net transverse magnetic moment (Mt). Upon termination of excitation field B1, signals are emitted by the excited spins.
In order to utilize these signals to produce a magnetic resonance (MR) image, the object of interest is also subjected to linear magnetic field gradients (Gx, Gy, and Gz). Typically, the object to be imaged is scanned by a sequence of measurement cycles in which these gradient waveforms vary according to the particular localization method being used. The linear gradients are configured to encode the emitted signals with spatial information such that the resulting set of received MR signals may be processed and reconstructed as a MR image.
When imaging anatomy located near the surface of a patient""s body, a surface radio frequency (RF) coil, which is fairly small in size, may be used to produce high quality MR images. Since the signal-to-noise ratio (SNR) is higher for smaller RF coils than for larger RF coils, such as, body RF coils, when only a small region of the patient""s body needs to be imaged, smaller RF coils can be used to produce the highest quality images. However, very small surface coils have a disadvantage in that they are difficult to position properly relative to the anatomy of interest. To facilitate repositioning of the surface coil, MR imaging systems are configured to permit an operator to have access to and interact with the patient positioned therein (generally referred to as open MR imaging systems). Accordingly, during a given procedure, the operator has the freedom to move in the vicinity of the patient and adjust the position of the surface coil relative to the patient""s body, as needed, without disturbing the patient""s position relative to the MR imaging system (i.e., without removing the patient from the magnet(s) of the MR imaging system).
Moreover, images acquired using a small surface coil correspondingly have a small field of view. Thus, when the operator is presented with such a small field of view image, it is very difficult for the operator to accurately identify the part of the anatomy being displayed. This would be analogous to the operator viewing a previously unseen room under low lighting conditions using only a narrow beam flashlight. He/she would have difficulty identifying where he/she is in the room and what he/she is looking at.
Still another shortcoming associated with surface coils is that when the surface coil is moved to a new location on the patient""s body, it is difficult to correctly position the surface coil relative to the acquisition slice. The surface coil should receive emitted MR signals from at least a prescribed acquisition slice to provide an image of the acquisition slice and not another region of the patient""s body. In other words, the images acquired should display anatomy located at the acquisition slice and such anatomy should be displayed at approximately the center of the images.
Thus, there is a need for a system and method that permits one or more movements or positioning of the surface coil relative to the patient during a given procedure without generating MR images with incorrect image locations. There is a further need for a system and method that overcomes the difficulty in anatomy identification due to small field of view images resulting from the use of surface coils.
One embodiment of the invention relates to a magnetic resonance (MR) imaging system including a surface coil configured to generate an MR image having an appropriate image location. The system includes a controller configured to automatically synchronize a position of an image acquisition plane with respect to a position of the surface coil. Each of the position of the image acquisition plane and the surface coil is defined by at least a location and an orientation.
Another embodiment of the invention relates to a method of generating a magnetic resonance (MR) image having an appropriate image location in an MR imaging system including a surface coil. The method includes monitoring a position of at least one of an image acquisition plane and the surface coil. The method further includes coordinating the position of the image acquisition plane with respect to the position of the surface coil. Each of the position of the image acquisition plane and the surface coil is defined by at least a location and an orientation.
Still another embodiment of the invention relates to a system for generating a magnetic resonance (MR) image having an appropriate image location in an MR imaging system including a surface coil. The system includes means for monitoring a position of at least one of an image acquisition plane and the surface coil. The system further includes means for coordinating the position of the image acquisition plane with respect to the position of the surface coil. Each of the position of the image acquisition plane and the surface coil is defined by at least a location and an orientation.